The present invention relates to a hub assembly for holding a replacable wheel where the hub assembly may be manually disassembled to release a previously-held wheel and reassembled to hold and to rotate a fresh wheel. The present invention more closely relates to such an assembly of demountable hub and wheel where wheel replacement is achieved with minimal manual intervention.
While the present invention is hereinafter described in relation to a hub and wheel assembly for use in a document moving track in a document encoder, it is not intended that this illustrated use should represent a limitation upon the application of the present invention which may be used in any situation where a wheel must periodically be replaced or removed, such as in office equipment, mechanical gear boxes, and for vehicular wheels. The present invention may be employed securely to hold any object which requires to be rotated about the axis or shaft.
In document encoding machinery such as is used for automated processing of check in banking, it is usual to employ a document track into which checks are fed one by one from a stack for automated processing as the checks pass along the length of the track. In order to avoid the inadvertent movement along the track of two or more checks together, it is the practice to provide in the track a pair of opposed rubber wheels one of which rotates with a small angular velocity and the other of which rotates with a high angular velocity. When a check passes therebetween, if there is only one check present it is gripped by the wheel of low angular velocity and the wheel of high angular velocity rubs at high speed against the other face of the check. If two or more checks come along the document track together, the wheel of high angular velocity engages the additional check or checks and projects them at higher speed along the document track to avoid the checks passing together along the track. Thus, the wheel of high angular velocity scrubs continuously against either the wheel of low angular velocity or the rear of a document to be processed. Only on very rare occasions when two documents come along the document track together is the wheel of high angular velocity free from scrubbing against objects moving much more slowly than itself and therefore free from the high attritional wear attendant thereon. The wheel of high angular velocity is therefore subject to frequent replacement as its dimensions and consequent elastic pressure in opposition to the wheel of low angular velocity are reduced by frictional attrition.
In the past, it has been the practice to provide as the scrub wheel of high angular velocity a wheel and hub assembly wherein a replacable wheel having an elastic tire fitted thereon is held on the hub, the hub consisting in a base member and a holding member. The holding member was attached to the base member to clamp the wheel between the holding member and the base member by means of displacable elastic arms having a clip at the distal end of each for engaging the base member. In order to remove the holding member it was necessary to use some kind of tool and two hands. The elastic arms of the holding member were liable to fatigue fracture making the life expectancy of the holding member very short in terms of the number of times that a wheel could be changed. The replacement of the wheel required to be undertaken by skilled personnel whose presence and time was costly. The amount of time during which a machine was out of use while its wheel or wheels were being changed was high.
Other mechanical arrangements for holding a wheel were envisaged. Each arrangement required the provision of complex machined parts, costly in themselves to produce.
It is, therefore, desirable to provide a wheel and hub assembly where replacement of the wheel is rapidly and readily achieved by unskilled personnel without the use of tools and without stress to the hub assembly so that the hub assembly may indefinitely be used to hold replacement wheels without risk of stress fractures. Further, it is desirable that the wheel and hub assembly be of a simple construction capable of being made in a low cost fabrication process such as moulding.